Undo not allowed

New case :

I'm creating a filter.
I haven't still done anything.
I have a Free Gradient that is detached from the Result.
I deleted the value of the End Y and I typed 0.
I deleted the value of the End X and I typed 0.
I tried to Undo, but Undo is gray color and can't be used.

GMM. I think the causes can be only three:

1. I still use Windows XP in this computer ( because of other old programs that can't run on Windows 8 ). Something it may not match perfectly with FF 4.

2. There is some of error in my FF installation.

3. I let is as last, because I guess you checked.
As it may be clear in my second message, it is not a problem of a specific filter.
That time I had only two components: Result and Free Gradient. They weren't even connected. Free Gradient was unable to undo after I changed to 0 ( I typed the numbers directly ) End Y and End X.
If you can't reproduce the same mistake in your computer, the cause is probably not FF itself but something else in my system.

Ramlyn, I guess you type a new value into a component and press Enter? This doesn't work as you expect
If you type a value, it is applied immediately, and you will be able to undo your action. On the other hand, pressing Enter removes the focus from the component. You need to click the component again to be able to undo the value change.

I'm not sure if this is intended behavior, will need to ask the devs. But it is easy to avoid: just don't press Enter.

Ok, now I see. This is definitely a bug, thanks for pointing it out. Clicking Edit removes the focus as well: please use Ctrl+Z instead (until the issue is fixed).

Note you can restore the focus by clicking on the component again to enable the Undo menu.